A PRELIMINARY REPORT ON CLAYS OE ELORIDA 
133 
COLUMBIA COUNTY 
Columbia County lies in the northeastern part of the State. The 
Alum Bluff formation is exposed at the surface in the northern two- 
thirds of the county and the Ocala formation in the southern one-third. 
Sandy surface clays of uncertain age cover a large part of the county. 
In some localities this material is desirable for sand-clay road material. 
South of the region about Lake City no clays of value are known as is 
also the case in the north and northeastern parts of the county. About 
six miles northeast of White Springs a very soft white shale is exposed 
on the Hamilton County side of the Suwannee River. For a detailed de¬ 
scription of this exposure see.page 165. This clay no doubt underlies 
adjacent portions of Columbia County as well. 
A green jointed clay overlain by four feet of brown, gray and white 
mottled sandy clay is exposed about two miles south of Lake City on the 
Gainesville road. The contact between these two clays is indistinct and 
the upper portion is probably a residual mantle. The thickness of the 
lower clay is unknown.' It has a high air shrinkage and cracks badly 
in drying and is therefore unsuited for use in manufactured products. 
The region between Lake City and White Springs is underlain 
by one or more beds of a greenish jointed clay. These beds are variable 
in thickness and are interbedded with sands and sandy clays. In places 
this clay contains calcareous concretions and in other places it contains 
some phosphatic material, it has a high air shrinkage, warps and cracks 
badly, and its plasticity is too low to work satisfactorily in a stiff mud 
machine. For a typical section of this clay see page 114. 
At a brick plant formerly operated about three miles southwest of 
Lake City a gray sandy clay occurs and was formerly used for common 
brick. Its low plasticity, low bonding strength and poor working quali¬ 
ties make it undesirable for any kind of manufactured clay product. It 
is still distinctly soft and porous at cone 15. It has the following physical 
properties: 
Physical Properties of Lake City Brick Yard No. I Clay (Lab. No. 0 - 36 ). 
Plasticity, judged by feel. Poor. 
Water of plasticity. 17.45% 
Pore water. 0.23% 
Shrinkage water. 17.22% 
Linear air shrinkage. 3.6% 
Volume air shrinkage. 7.92% 
Modulus of rupture, average. 121.0 pounds per square inch. 
Slaking test. 30 hours. 
